(1) Field of the Invention
The present invention relates to an improvement in an intake pipe for communicating a carbureter and an intake port of a cylinder of an internal combustion engine such as a two-cycle engine.
(2) Description of the Prior Art
Conventionally, such an intake pipe has been typically provided with a smooth inner wall surface. This known type intake pipe has been widely used in general.
In case of the intake pipe having a smooth inner wall, when a throttle valve is abruptly returned from a full throttle condition back to an idle operation, the intake inertia causes the supplied amount of fuel to be temporarily excessive. As a result, the engine would be stalled. In order to avoid such a phenomenon, it is necessary to make leaner a carburetor set value upon the idle operation than that during the normal operation. This makes it possible to prevent the engine from stalling when the throttle valve is abruptly returned back to the idle operation, but inversely an acceleration performance would be suppressed. In order to solve this incompatible problem, it has been proposed to provide an intake pipe with a number of continuous pleats in a circumferential direction as shown in Japanese Utility Model Unexamined Publication No. 51009/1985. However, this has not yet been satisfactory.